# Terminator in Raspberry Pi CAN-shield

I am planning to connect (at least) two Raspberry Pi + PiCAN2 shields via CAN.

I think I understand the concept of a daisy-chained multidrop CAN line, but what about using the 120 ohm resistors for termination that are provided on board by the PiCAN2 shield?

As far as I understand when I simply connect CAN High and CAN Low respectively between both PiCAN2 shields A and B as shown below, I should use the 120 ohm resistors on both sides for termination. Am I right?

What happens when I add a third identical node (Raspberry Pi + PiCAN2 shield) C to the CAN bus? Do I need to terminate also on this node? As I can without problems also use the terminator on C, is there any drawback to using the 120 ohm resistor on all nodes, not worrying about the geometry of the network?

simulate this circuit – Schematic created using CircuitLab

• no termination is required if the stub is really short, which it should be .... the wire should really go from A to C to B without a stub at C ..... with a long stub, it would not be a daisychain, but it would be a star network May 29 '18 at 21:52
• @jsotola: Referring to the star network with a long stub to C. Would this require a terminator? May 29 '18 at 22:00
• You need termination only at A and B ...no termination at C. In fact you could have multiple PICAN2's in the middle and none of them would need terminators. You don't have a Star network as shown, you have a bus network. Read this: en.wikipedia.org/wiki/CAN_bus May 29 '18 at 22:25
• @JackCreasey, You don't have a Star network as shown ... there is no mention of the length of the stub at C .... if it is long then the network is a star network and requires termination at C May 30 '18 at 1:13

• Thanks a lot for your answer! I have one question regarding this sentence, which I do not understand: Extra terminators, especially near the center of the bus, have more of an effect of the maximum number of nodes before noise sensitivity gets poor. Does the use of Termination on Node C have any negative side effect? May 30 '18 at 8:01